Dehumidifying system



v Nov.,18, 1941. R p MATTERN ETAL 2,262,954

DEHUM IDIFY I NG SYS T EM Filed March 30, 1938 2 Shets-Sheet 1 124- Fig. 1

INV'ENTOR s Raymond RMa ttern Willi am L.McGrath AT ORNEY NOV- 18, 1941. MATTERN HAL 2,262,954

DEHUMIDIFYING SYSTEM Filed March so, 1938 2 Sheefs-Sheet 2 INVENTOR Raymond RMattern WiLliamL-Mc' ra th Patented Nov. 18, 1941 -UNI TED STATES PATENT OFFICE 2,262,954 nenummrrrnvc SYSTEM Raymond P. Mattern, Minneapolis, and William L. McGrath, St. Paul, Minn., assignors to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn a corporation of Delaware Application March 30, 1938, Serial No. 198,986

6 Claims.

' spray a solution of hygroscopic element, such as lithium chloride into th air to be dried, thereby removing an amount of moisture, this amount being dependent upon the concentration of the hygroscopic fluid, and to maintain the hygroscopic fluid sufliciently concentrated by circulating the same or a portion of the same through a regenerator, in which some of the water vapor is driven off from the solution. In order that the hygroscopic fluid does not freeze or become crystallized after it has been regenerated, care must be taken that the concentration of the solution does not rise above a definite value, which value depends upon the particular hygroscopic element which is used.

One of the objects of our invention is the provision of an improved control system for a dehumidifying system of the type above discussed.

More specifically, it is an object of the invention to provide a device by which,the concentratiolnfof the hygroscopic fluid is measured by compa ng it with a solution of known concentration, and by such device to control the amount of heat to the regenerator to maintain the concentration at a flxed amount.

A further object is the provision of an improved device for measuring the concentration of a solution.

Another'object is to provide, in a system of the type above described, improved control means including a humidity controller for controlling the supply of heat to the regenerator in a manner to maintain a substantially constant humidity in the space to be controlled, and a, device. responsive to the concentration of the solution acting as a limit control to reduce the supply of heat to the regenerator should the concentration rise to a predetermined value.

Another object of this invention is the provision of improved control means for a dehumidifying system of the type described, wherein the heat supply to the regenerator is controlled by a device responsive to the concentration of the solution being sprayed into the air to be dehumidified, and a space humidity responsive devioealso in control of the heat supply compensating the effect of the solution concentration responsive device. I

A further object of the invention is in the provision of an improved means for maintaining the concentration of a solution at a fixed value by means of a device having two compartments separated by a wall including osmotic material, a liquid of known concentration in one compartment, the solution to be controlled in the other compartment, and operating the concentration changing means in accordance with the varying osmotic action of the liquid occasioned by the varying concentration of the concentrated solution.

Further objects will become apparent upon an examination of the specification claims and drawings, in which like reference characters represent like parts in the two views, and in which,

Figure 1 is a diagrammatic view of one form, of the system embodying our invention;

Figure 2 is a diagrammatic view of another form of system embodying our invention;

Figure 3 is a modification of a portion of the structure shown in Figures 1 and 2; and

Figure 4 is a section taken in the direction of the arrows on line H of Figure 3.

Referring to Figure 1, an air conditioning chamber is represented by the reference character III. This chamber may include a fresh air inlet II, a return air inlet l2, a fan l3 driven by a motor II for drawing air through the chamber In and exhausting it through a discharge outlet l5 into a space it. The proportion of fresh and return air drawn into the chamber In through inlets II and I2 may be controlled by dampers l1 and I8, respectively. These dampers may be manually operated or automatically operated in any well known manner.

A spray 20 is located in the chamber In at a point where the fresh and return air entering the chamber is mixed, suitable hygroscopic fluid being sprayed into the chamber ill by the spray 20 for removing moisture from the air within the chamber. The removal of moisture by hygroscopic fluid is accompanied by an' increase in the temperature of the air from which the moisture is removed and a cooling coil 2| is provided to reduce the temperature of the air within the chamber before it is passed into the space It by thefan l3. Any suitable cooling medium may be passed through the coil 2|, a valve 22 being provided to control the flow of the cooling medium through the cooling coil. Valve .22 may include a valve stem 23 to which is connected'a rack 24 cooperating with a pinion 25 which is driven by a motor 26.

Motor 26'may be a proportioning motor of the type shown in Patent 2,028,110 issued January 1936, to D. G. Taylor. Such a motor includes a pair offleldwindings selectively energized for causing rotation of the motor in one direction or the other. For controlling the energization ofjthe'two fleld windings, the motor includes a pair of balanced opposed relay coils which are connected together at one end, the junction of these coils being connected to terminal 3| located on the outside. of the motor. Terminals 38 and 32 are connected to the opposite ends of these relay coils. 'Power maybe supplied to the motor through conductors 33 and 34 which lead to any suitable source of power (not shown). A thermostat 35 may be locatedin the space |6 or if desired could be.,located in the return air duct l2 and "this thermostat may include a bimetallic-element and an arm 31 carried thereby and passing over a resistance element 38 in response to changes in temperature in the space l6. The bimetallic element--36 is connected by conductor '39 to the terminal 3| of the motor which is connected to the junction of the aforedescribed relaylcoils. Conductors 48 and 4| connect the ends or the resistance 38 to the opposite ends of the relay coils by means of terminals 30 and 32. The opposite ends of these relay coilsare-alsoconnectedto the conductors 33 and 34 leading to the source of power. As the arm 31 of thermostat 35 passes over the resistance 38, the resistance in parallelwith one relay coil will increase while. the resistance in parallel to the other relay coil will decrease, thus causing the energization of one of the fleld windings and causing a rotation of the motor in one direction. A second potentiometer coil is included in the motor 26 and is connected in parallel with the potentiometer 38 to the relay coils. The arm of this potentiometer is driven by the motor 26 and moves in reverse relationship with respect to the arm 31 of thermostat 35 so that after the arm of this potentiometer has moved a distance corresponding to the movement of arm 31 over resistance 38, the resistance inparallel with the relay coils will become equal, the relay coils will be equally energized, and the motor 26 will come to rest. It will, therefore, be seen that the amount of opening of the valve 22will be proportional to the-extent of movement ofarm 31 over resistance 38, or in other words, proportional to the temperature change in the space l6, the arrangement being such that as the temperature in the space increases, and arm 31 moves to the right, valve 22 moves towards open position and in response to a decrease in temperature in the space. and movement of arm 31 to the left, the valve 22 moves in ,the reverse direction. I

A pump 45 driven by a motor 46 is provided v for supplying a suitable hygroscopic fluid to the understood that the fluid passing from chamber Hi into regenerator 65 is relatively weak, having picked up a certain amount of moisture from the air, which moisture is driven off by the steam coil 66, this moisture passing through a pipe 15 and through a coil 15'uin the heat exchanger 6| whereby the fluid flowing into the regenerator 65 is preheated. The now-concentrated fluid leaving the regenerator 65 passes through outlet pipe 16, some of the fluid flowing through a pipe 11 into a heat exchanger 18, the rest of the fluid flowing through pipe 19 into the heat exchanger 63. The fluid flowing through pipe '19 will be relatively hot compared to the fluid flowing through pipe 62 so that the weak fluid flowing into the regenerator 65 is further. preheated in the heat exchanger 63. The flow of fluid into the heat exchanger 18 may be controlled by a valve 88. A coil 8| is mounted within the heat exchanger 18 and water flows into this coil through a; pipe 82 leaving the same through a pipe 83 whence it flows through a valve 84 to outlet 85. The now concentrated fluid which has passed through the heat exchanger 18 from the regenerator 65 flows through a pipe 86 to outlet 81.

A tank 98 is formed into compartments 9| and 92 by awall 93. This wall includes a portion 94 formed of a suitable osmotic material. This material may be formed by precipitating copper ferrocyanide on a wall of unglazed porous material or may be formed in any other known suitable manner. The compartment 92 is filled with the concentrated fluid and may be allowed to overflow and empty into another co'mpartment formed by a .wall 95 which empties into a pipe 96 leading to a pipe 91 which is connected to the heat exchanger 63. A suitable outlet 98 is provided in the bottom oii compartment 92 to allow the fluid in said compartment to flow out so that the fluid in this compartment is constantly being replaced by fresh concentrated fluid. Valve 84 is controlled by a suitable float |0| resting on the surface of the water in compartment 9|, this float being operatively connected to the valve 84 by means of a pivoted lever I82. A suitable outlet Hill is provided at the bottom of the compartment 92 containing concentrated fluid by the three-way mixing valve 52 whence it flows through pipe 53 to the inlet of pump 45, the fluid then being pumped through a pipe 54, a cooler and a pipe 56 to the spray 26. Cooler 5 may be supplied by means of pipe with any suitable cooling medium in order to reduce the temperature of the hygroscopic fluid so that well known principle of osmosis, the rate of flow through the wall portion 94' depending upon the concentration of the fluid in compartment 92. Float IN is intended to control the valve 84 to' maintain the amount of water in compartment 9| substantially constant. In otherwords, the amount of water issuing from outlet should be equal to the amount of water leaving"the tank through pipe I88 plus the amount ofvwater passing through wall portion 94 into compartment 92. Should now the concentration of the fluid in compartment 92 increase, the water will flow through the wall portion 94 at an increasin v rate so that the water will leave the compartment 9| faster than it enters the same, whereupon the float |0| begins to drop thus causing valve 84 to open, admitting more water to the compartment through outlet 85. The movement of this float may be utilized to control the operation of motor I3 and therefore the valve 68 controlling the steam supplied to the regenerator in a manner to prevent the concentration of the fluid leaving the regenerator from exceeding such a high value that the hygroscopic fluid begins to crystallize or freeze, as will be hereinafter explained.

Also mounted within the space I6 is a suitable humidity responsive device generally indicated by the reference character I05. This device may include a humidity responsive element I06 of any suitable character such as hairs, element I06 being connected at its upper end to a lever I01 and at its lower end to a second lever I08. The position of lever I01 may be suitably adjusted by means of an adjusting screw I08. Lever I08 is pivoted on a suitable pivot I I0, a spring III urg-.

ing the right-hand portion of the lever I08 upwardly and thus tending to stretch the humidity responsive element I06. Element I06 becomeselongated as the humidity within the space increases whereupon the right end of lever. I08 is caused to move upwardly by means of the spring III, and upon a decrease in humidity within the space I6 the humidity responsive element I06 contracts and the right end of lever I08 moves downwardly against the force of spring II I.

nected between terminals I2I and I22, thus causing motor I3 to rotate in such a direction as to increase the opening of valve 68 in accordance with the increase in humidity in the space wherev,

upon more steam is supplied to the regenerator 65 and the concentration of the fluid leaving the regenerator 65 is increased. Should the concentration of this fluid be raised high enough, it would crystallize which is, or course, undesirable in such a system. An increase in concentration will cause an increase in the flow of water through increase until the water entering the compartance I I6 is connected by means of conductors I II V and H8 to'the motor terminal I20 which is connected to the end or one'of the relay coils in the same manner as terminal 32 of motor 26. The other end of resistance I I6 is connected by means of conductors I23 and I24 to the terminal I 22 of motor I3 connected to the end of the other relay coil of the motor. A second resistance I25 is arranged to be engaged by an arm I26 con- .nected to the float carrying arm for movement ment is equal to the water leaving the compartment. The movement of arm I26 downwardly over resistance I25 results in resistance being interposed between the terminal I2I of motor 13 and the arm 5 of humidity responsive device I05, thus desensitizing the effect of the resistance I I6 over the motor I3 and decreasing the amount of resistance in parallel with the coil between the terminals I2I andI22-of the motor, whereupon the. motor I3 rotates in a direction to move the vawesa towards closed position until the balancing potentiometer within the motor has balanced the combined effects of resistances I25 and I I6 on the motor I3, The desensitizing of the effect of sistance I25 is connected by means of a conductor I30 to the arm II5 which passes over resistance 6. With the arm I26 in the extreme upper position of the resistance I25, it will be seen that potentiometer II6 forms the controlling potentiometer for the motor I3, being connected in parallel with the relay coils thereof so that movement of arm II5 over the resistance element II6 causes rotation of motor I3 in one directionor the other an amount corresponding to the amount of movement of the arm II5 over resistance I16. The lower portion or resistance :I25 is connected by means of conductors I32 and I24 to the motor terminal I22 so that resistance I25 is in parallel with the relay coil connected between terminals I2I and I22 when arm I26 is in its extreme upper position, as shown. In order that this resistance will have no efl'ect on the motor I3 with the arm I26 in the position illustrated. a resistance elevment I35 having a resistance value equal to the value of the resistance I25 is connected by means of conductors "H8 and-I28 to the terminals I20 and I2I so that with the arm [26 in the position the controller II6 on the motor has-the effect of raising the control point of the humidity respone sive device-so that a higher humidity will be maintained in the space, this control point increasing as the-concentration of the fluid within compartment 92 increases. Resistance I25 thereby acts as a limit controller whereby the concentration of the hygroscopic fluid is never permitted to rise above a predetermined value. The arml26 may cooperate with a suitable scaleto give a visual indication of the degree of concentration of the solutionin compartment 02.

In a system of this type, it is generally necessary to pass only a portion of the hygroscopic fluid through a regenerator and the amount that by the valve member 52 In the form of invention shown in Figure 2, the flowuf steam to the regenerator is controlled is to be passed therethrough is suitably controlled directly by the concentration of the hygroscopic shown, the motor is controlled solely, by the humidity responsive device I 05.

If the humidity in the space I6 increases indicating that more moisture should be removed from the air, arm II5 will be caused to moveupwardly over resistance .II 6 thus decreasing the fluid and the concentration of the fluid is varied in accordance with the humidity in the space I6, instead of controlling the concentration in accordance with the humidity in the space and utilizing the float. IOI asa limit control over the steam valve 68 as ih,.Figure l. The piping arrangement of the system in this figure is the 'same as that in Figure l except that the fluid in compartment 92 is the mixture of the regenerated and the unregenerated hygroscopic fluid, the connectionbeing taken at the point where pipe 56 connects to the spray 20.

Th arm I26 which passes over resistance I25 in Figure 1 is-replaced by a lever I pivoted at I5l and connected to the float :by means of pivot I52. The left portion of this lever passes over a resistance I53 and the opposite extremity of the lever passes over a resistance I54, This latter resistance is tappeiPat its center and is connected to the terminal I2I of motor 13 by means of conductors I and I56. The arm II5 of the humidity responsive ;device I05 is con nected to the terminal I 2 I of the motor I3 through I conductors I55, I51, resistance element I59 and conductor I59, resistance I58 being an adjustable resistance. The upper end of resistance IIG is ,connected by means of conductors I60 and I5I. to 5 the motorv terminal I whereas the lower portion of resistance H5 is connected by means of conductors I62 and I63 to the terminal I22. The upper end of resistance I53 is connected to the motor terminal I20 by means of conductors IIM l0 and IBI and th lower portion of this resistance is connected to the terminal I22 by means of conductors I51 and I53. It will, therefore be apparent that the potentiometers H6 and I53 are connected in parallel to each other and to 15 the relay coils of the motor 13, the motor being provided with a balancing potentiometer as in, Figure 1 to balance the efiect of these two potentiometers. By reason of the resistance I55 connected between terminal I2I and control arm 2() H5 of potentiometer IIB, this potentiometer is less sensitive than potentiometer I53 In other words, for a small amount of movement of-arm I I50, arm I I5 must move through the entire range of its movement to affect the motor I3 to the 25 same extent. The. control range of the arm I50 to caus the motor 13 tomove between fully opened and fully closed position is represented by the reference character X.

As 'the concentration of the fluid within compartment 92 changes, thus causing movement of the float IOI up or downf'the motor I3 is caused to move towards open or closed position an amount corresponding to the movement of the float IN, or in other words, to the amount of '35 movement of arm I over the resistance I53.

It now the humidity in the space I0 should increase, thus causing movement of arm II5 upwardly over resistance I III, the resistance in parallel with the relay coil between terminals I20 40 and I2I will decrease thus causing the motor to rotate in adirection to open the steam valve 68 more widely. The control point of the potentiometer I53 will now be shifted downwardly so will be moved downwardly over resistance I I9 so 55 that the control point of potentiometer I53 will be shifted upwardlywhereby the concentration of the fluid in compartment 92 will be maintained at a lower, value, it being remembered that as the concentration of the fluid in compartment 0 92 increases th level of the fluid in'compartment 9| decreases for agiven rate of flow of fluid into this compartment.

It is therefore, apparent that in this form of the invention, the main control function is per- 5 formed by the float IN. and is compensated by the control" I05 so that the concentration of the fluid being used for. dehumidification will be increased as the humidity in the spac I6 increases and will decrease as the humidity decreases. The 1 various' resistances maybe so chosen that when the control arm U5 is in the extreme upper por-' tion; of resistance II5 indicating an excessive humidity in the space the control point of the potentiometer I53 will be such that the concentration of the hygroscopic fluid will never exceed a value that will cause crystallization of the fluid.

In Figures 3 and 4, a modification of the tank is illustrated wherein the necessity-of using a' valve for controlling the supply of water to the compartment'QI is eliminated. In Figures 1 and 2, the osmotic portion 94 of the wall separating 'the compartments terminated a substantial distance below the top of this wall, the liquid normally rising above the upper extremity of the osmotic portion 94. As the concentration of the solution in compartment 92 increases and the flow of water from compartment 9| into compartment92 correspondingly increases, the level of the water in the compartment 9| 'will gradually drop if the amount of water being! supplied to the. compartment is not increased,

and for this reason it was necessary to provide upperextremity of the osmotic portion "5 and 'the water is fed into compartment 9I at the same rate at all times. If the concentration of the solution in compartment 92 increases, the

rate of flow of the water from compartment 9I into compartment 92 will likewise increase and since the water is flowing from the compartment through outlet I00 at a uniform rate, it will be apparent, that the water is flowing out of the compartment 9| faster than it is flowing into the compartment. As the level of the water starts to decrease, the portion of the osmotic portion "5 which is available for permitting the passage of water from compartment 9I into compartment 92 wil become less and finally the level of the water will drop to such an extent that the amount of water flowing from compartment 9I into compartment 92 will be substantially concentration of the solution in compartment 92 has increased, permitting the water to flow throughthe portion I15 of the wall separating the compartments at a faster rate, there is a lesser portion of this wall portion "5 available for the water to flow through as the level of the water drops, so that the increase in the rate 'of flow per unit area through wall portion, I15 is compensated for by the decrease in the available portion of this wall through which the water may flow.

It is, therefore, unnecessary to vary the flow of water into tank 9I as the concentration of the solution in compartment 92 increases and the sole function of the float IOI is thereforelglo oper-' ate the arm I25 of Figure l or I50 0 g. 2 to vary the amount 'of steam supplied to the regenerator in the same manner as in Figures 1 and 2.

It will, thereforefbe apparent that the tank of Figures 3 and 4 with anosmotic wall portion of triangular shape/may be substituted for the tank ,1

operate with a suitable scale to give a visual concentration of the solution in compartment 92.

While the fluid being fed into compartment 9| has been described as water, it will be apparent that any suitable solvent for the hygroscopic element in solution in compartment 92 may be fed into the compartment 9|. It will also be apparent that the fluid being fed into the compartment 92 in the form of the invention of Figure 2 need not necessarily be taken from the point" illustrated but any other suitable point may be chosen.

Having described the preferred forms of our invention it will be apparent that many modiflcations may become apparent to those skilled in the art, and itshould thereiore'be understood that our invention is limited only by the scope of the appended claims.

We claim as our invention:

1. In a chemical 'dehumidifying system for controlling the humidity of a space, means utilizing a hygroscopic fluid for removing moisture from the air in said space, regenerating means for increasing the concentration of the hygroscopic fluid after it has become dilute by absorbing moisture from the air, said regenerating means including means for heating at least aportion of the hygroscopic fluid us'ed'in the system, electrically operated means in' control "of the heating means to vary the heating efl'ect' thereoi', means for controlling the operation of said electrically operated means including flrst and second variable resistance means, means responsive to the humidity of the air in the space in control of one of said resistance means and means, responsive to the concentration of the. hygroscopic fluid in control of the other resistance means.

2. In a chemical dehumidifying system for controlling the humidity of a space, means utilizing a hygroscopic fluid for removing moisture from the air in a space, regenerating means for increasing the concentration of the hygroscopic fluid after it has become dilute by absorbing moisture from the air, means including electrical proportioning means responsive to the concentration of the hygroscopic fluid being delivered to the point of utilization thereof for graduatingly controlling the operation of the regenerating means, and means responsive to the humidity of the air in the space electrically connected with to the point of utilization thereof, for graduatingly controlling the regenerating means to main.- tain the concentrationthereoi within predetermined limits, and meansresponsive to the humidity of the air in the space electrically connected with said proportion ing means for ad-,

, creasing the concentration of the hygroscopic fluid after it has become dilute by absorbing moisture from the air, said regenerating means including means for heating at least-a portion of the hygroscopic fluidused in the system, and means for controlling the heating means to control the concentration of the hygroscopic fluid, said means including means responsive to the humidity of the air in the space and means responsive to the concentration of the hygroscopic fluid, said last named means including means responsive to the rate of flow between the hygroscopic fluid and a fluid of known concentration through an osmotic wall.

5. In a chemical dehumidifying system for controlling the humidity of'a space, means utilizing a hygroscopic fluid for removing moisture from the air in a space, regenerating means for increasing the'concentration of the hygroscopic fluid after it has become di1ute"by absorbing moisture from the air, said regenerating means including means for heating ,at least a portion of the hygroscopic fluid usedin the system, a chamber divided by a' wall, having at least a portion thereof formed of osmotic material, into two compartments, means for feeding hygroscopic fluid. into one of said compartments and maintaining said fluid at a constant level, means for feeding a solvent of known concentrationinto the other compartment, means controlling the flow ofsolvent' into said other compartment in accordance with the rate of flow of the solvent; through said wall, means controlled by the flow.

controlling means for controlling the heating means, and means responsive to the humidity in a hygroscopic fluid for removing moisture from the air in a space, regenerating means for increasing the concentration of the hygroscopic fluid after it has become dilute by absorbing moisture from the air, said regenerating means including means for heating at least a portion of the hygroscopic fluid used in the system, a,

chamber divided by' .a wall, havingat least a" portion thereof'formed' of osmotic material, into two compartments, means for feeding hygro-'=- scopic fluid into one of said compartments and maintaining said fluid at a constant level, means for feeding a solvent of known concentrationv into the other compartment, means controlling the flow 'of solvent into said other compartment in accordance with the rate of flow of the solvent through said wall, means controlled by the 'flow controlling means for controlling the heating means to maintain the concentration of the hygroscopic fluid in said one compartment between predetermined limits, and means responsive to the humidity of the air in said space for adjusting said limits in accordance with a pre- 

